Biochar: an alternative to activated carbon for the establishment of perennial ryegrass

Authors: Trippe, Kristin; MEYER, KYLIE - Oregon State University; Watts, Donald - Don; Novak, Jeffrey; Garcia-Jaramillo, Manuel

Submitted to: Seed Production Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2021
Publication Date: 4/30/2021
Citation: Trippe, K.M., Meyer, K., Watts, D.W., Novak, J.M., Garcia-Jaramillo, M.N. 2021. Biochar: an alternative to activated carbon for the establishment of perennial ryegrass. Seed Production Research. 50-53.

Interpretive Summary: The ability to produce seed crops that are free of weed seed is vital to meeting consumer demand, export restrictions, and certification requirements. In the Willamette Valley, the ongoing challenge to produce weed-free grass seed is sometimes met by carbon seeding, a practice that allows producers to establish crops by applying a narrow band of activated carbon (AC) directly over the seed, followed by treatment with a preemergent herbicide. The AC provides crop safety by absorbing the herbicide, essentially deactivating it within the planting row. While this method is generally effective, the combined cost of the AC and the chemical control limits its feasibility. Biochar, or charcoal that is added to soil, is produced from the combustion of low-value feedstocks. Biochar is known to bind a wide spectrum of compounds, including herbicides. However, biochar:herbicide interactions vary according to the physical and chemical properties of the biochar and the herbicide. Therefore, it is important to evaluate the interactions between specific biochars and specific herbicides on a case-by-case basis. In some instances, biochar can behave similarly to AC; as such, this study evaluated whether biochar could be a low-cost substitute for AC in carbon seeding applications. In the current study, we present the preliminary results of a greenhouse study that evaluates the level of crop safety provided by barley, juniper, or a mixed-conifer biochar towards three herbicides commonly used in carbon banding practices: diuron, indaziflam (Alion®), or a mixture of flumioxazin + pyroxasulfone (Fierce®). In general, we found that a mixed-conifer biochar (Rogue Biochar®) and activated carbon provided similar levels of plant safety, while the plant safety provided by juniper and barley-based biochars were dependent on the herbicide. Further studies that examine the binding capacities, mechanisms, and efficacy of these biochars under field conditions are currently underway.

Technical Abstract: The ability to produce seed crops that are free of weed seed is vital to meeting consumer demand, export restrictions, and certification requirements. In the Willamette Valley, the ongoing challenge to produce weed-free grass seed is sometimes met by carbon seeding, a practice that allows producers to establish crops by applying a narrow band of activated carbon (AC) directly over the seed, followed by treatment with a preemergent herbicide. The AC provides crop safety by absorbing the herbicide, essentially deactivating it within the planting row. While this method is generally effective, the combined cost of the AC and the chemical control limits its feasibility. Biochar, or charcoal that is added to soil, is produced from the combustion of low-value feedstocks. Biochar is known to bind a wide spectrum of compounds, including herbicides. However, biochar:herbicide interactions vary according to the physical and chemical properties of the biochar and the herbicide. Therefore, it is important to evaluate the interactions between specific biochars and specific herbicides on a case-by-case basis. In some instances, biochar can behave similarly to AC; as such, this study evaluated whether biochar could be a low-cost substitute for AC in carbon seeding applications. In the current study, we present the preliminary results of a greenhouse study that evaluates the level of crop safety provided by barley, juniper, or a mixed-conifer biochar towards three herbicides commonly used in carbon banding practices: diuron, indaziflam (Alion®), or a mixture of flumioxazin + pyroxasulfone (Fierce®). In general, we found that a mixed-conifer biochar (Rogue Biochar®) and activated carbon provided similar levels of plant safety, while the plant safety provided by juniper and barley-based biochars were dependent on the herbicide. Further studies that examine the binding capacities, mechanisms, and efficacy of these biochars under field conditions are currently underway.